Solar cell module

ABSTRACT

A solar cell module including: a solar cell; a first protection member provided on the light receiving surface side of the solar cell; a second protection member provided on the rear surface side of the solar cell; an encapsulant layer, including a first encapsulant layer disposed between the solar cell and the first protection member, and a second encapsulant layer disposed between the solar cell and the second protection member, which seals the solar cell; and a wavelength conversion substance, contained in at least the first encapsulant layer, which absorbs light having a specified wavelength, and converts the wavelength. The concentration of the wavelength conversion substance is higher in the first encapsulant layer than in the second encapsulant layer, and a resin constituting the second encapsulant layer has a smaller diffusion coefficient of the wavelength conversion substance than the diffusion coefficient of a resin constituting the first encapsulant layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.15/374,291 filed Dec. 9, 2016, which is a continuation under 35 U.S.C. §120 of PCT/JP2015/002621, filed May 25, 2015, which is incorporatedherein by reference and which claimed priority to Japanese PatentApplication No. 2014-122136 filed on Jun. 13, 2014. The presentapplication likewise claims priority under 35 U.S.C. § 119 to JapanesePatent Application No. 2014-122136 filed on Jun. 13, 2014, the entirecontent of which is also incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a solar cell module.

BACKGROUND

There is known a solar cell module including a wavelength conversionsubstance that absorbs light having a specified wavelength, and convertsthe wavelength. According to this solar cell module, light having awavelength region that makes little contribution to power generationamong incident light can be converted into light having a wavelengthcontributing greatly to power generation. For example, Patent Literature1 discloses a solar cell module in which an encapsulant layer containinga wavelength conversion substance therein is disposed on the lightreceiving surface side of a solar cell.

CITATION LIST Patent Literature

Patent Literature 1

WO 2011/148951 A

SUMMARY

In the solar cell module, light is mostly incident from the lightreceiving surface side, and therefore the wavelength conversionsubstance is preferably disposed on the light receiving surface side ofthe solar cell from a viewpoint of improvement of wavelength conversionefficiency. However, there is a case where the wavelength conversionsubstance is diffused on the rear surface side of the solar cell by longterm use of the solar cell module, and the concentration of thewavelength conversion substance on the light receiving surface side isreduced.

An aspect of a solar cell module according to the present disclosureincludes: a solar cell; a first protection member provided on a lightreceiving surface side of the solar cell; a second protection memberprovided on a rear surface side of the solar cell; an encapsulant layerthat includes a first encapsulant layer disposed between the solar celland the first protection member, and a second encapsulant layer disposedbetween the solar cell and the second protection member, and seals thesolar cell; and a wavelength conversion substance that is contained inat least the first encapsulant layer, and that absorbs light having aspecified wavelength, and converts the wavelength, wherein concentrationof the wavelength conversion substance in the first encapsulant layer ishigher than concentration of the wavelength conversion substance in thesecond encapsulant layer, and resin constituting the second encapsulantlayer has a smaller diffusion coefficient of the wavelength conversionsubstance than the diffusion coefficient of resin constituting the firstencapsulant layer.

In an aspect of the solar cell module according to the presentdisclosure, a diffusion inhibiting layer constituted from a materialhaving a smaller diffusion coefficient of the wavelength conversionsubstance than the diffusion coefficient of resin constituting the firstencapsulant layer is provided between the first encapsulant layer andthe second encapsulant layer.

According to a solar cell module of the present disclosure, a wavelengthconversion substance disposed on the light receiving surface side of asolar cell can be inhibited from being diffused on the rear surface sideof the solar cell.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a solar cell module of a first embodiment.

FIG. 2 is a sectional view of a solar cell panel constituting the solarcell module of the first embodiment (wiring materials are omitted).

FIG. 3 is a sectional view of a solar cell panel constituting a solarcell module of a second embodiment (wiring materials are omitted).

FIG. 4 is a plan view illustrating an extracted diffusion inhibitinglayer of FIG. 3.

FIG. 5 is a sectional view of a solar cell panel constituting a solarcell module of a third embodiment (wiring materials are omitted).

DETAILED DESCRIPTION

Hereinafter, an example of embodiments will be described in detail withreference to the drawings.

The drawings referred to in the embodiments are schematicallyillustrated, and the dimension ratios of components illustrated in thedrawing are sometimes different from the dimension ratios of realcomponents. Specific dimension ratios and the like should be determinedin consideration of the following description.

In this specification, a “light receiving surface” of each of a solarcell module, a solar cell, and a photoelectric conversion section meansa surface on which light is mainly incident (incident from a lightreceiving surface upon which 50% to 100% of light is incident), while a“rear surface” means a surface opposite to the light receiving surface.Additionally, description that “a second member is provided on a firstmember” does not means only a case where the first and second membersare provided so as to be in direct contact with each other, unlessotherwise mentioned. That is, this description includes a case whereanother member exists between the first and second members. Descriptionof “substantial . . . ” is intended to include not only “entirelyidentical” but also “substantially the same”, when “substantially thesame” is taken as an example.

First Embodiment

Hereinafter, a solar cell module 10 of a first embodiment will bedescribed in detail with reference to FIG. 1 and FIG. 2.

FIG. 1 is a sectional view of the solar cell module 10 which is anexample of the embodiment.

As illustrated in FIG. 1, the solar cell module 10 includes solar cells11, a first protection member 12 provided on the light receiving surfaceside of the solar cells 11, a second protection member 13 provided onthe rear surface side of the solar cells 11, and an encapsulant layer 14that seals the solar cells 11. The encapsulant layer 14 includes anencapsulant layer 14 a (first encapsulant layer) disposed between thesolar cells 11 and the first protection member 12, and an encapsulantlayer 14 b (second encapsulant layer) disposed between the solar cells11 and the second protection member 13.

The solar cell module 10 includes wavelength conversion substances 30contained in at least the encapsulant layer 14 a (refer to FIG. 2 andthe like described below). The wavelength conversion substances 30 aresubstances that absorb light having a specified wavelength to convertthe wavelength, and play a role in converting light in a wavelengthregion hardly contributing to power generation into light in awavelength region contributing greatly to power generation.

In this embodiment, a plurality of the solar cells 11 are disposed onsubstantially the same plane. The adjacent solar cells 11 are connectedin series by wiring materials 15, thereby forming a string of the solarcells 11. For example, each wiring material 15 bends in the modulethickness direction between the adjacent solar cells 11, and is mountedon an electrode on the light receiving surface side of one of the solarcells 11 and an electrode on the rear surface side of the other solarcell 11 by an adhesive or the like.

The solar cells 11, the first protection member 12, the secondprotection member 13, and the encapsulant layer 14 constitute a solarcell panel 16. The solar cell panel 16 is a plate-like body in which astring of the solar cells 11 are disposed between the respectiveprotection members, and has, for example, a substantially rectangularshape in plan view (when viewed from the direction perpendicular to thelight receiving surface). A frame 17 is preferably mounted on an endedge of the solar cell panel 16. The frame 17 protects the end edge ofthe solar cell panel 16, and is utilized when the solar cell module 10is installed on a roof or the like.

The solar cells 11 each include a photoelectric conversion section thatgenerates carriers by receiving light. Each solar cell 11 has a lightreceiving surface electrode formed on the light receiving surface of thephotoelectric conversion section and a rear surface electrode formed ona rear surface, as electrodes for collecting the carriers generated inthe photoelectric conversion section. However, the structure of eachsolar cell 11 is not limited to the above, and may be, for example, astructure in which an electrode is formed only on the rear surface ofthe photoelectric conversion section. The rear surface electrode ispreferably formed to have a larger area than the light receiving surfaceelectrode, and it can be said that the surface having a lager electrodearea (or a surface with an electrode formed thereon) is the “rearsurface” of the solar cell 11.

The photoelectric conversion section has, for example, a semiconductorsubstrate, an amorphous semiconductor layer formed on the substrate, anda transparent conductive layer formed on the amorphous semiconductorlayer. Examples of a semiconductor constituting the semiconductorsubstrate can include crystalline silicon (c-Si), gallium arsenide(GaAs), indium phosphide (InP) and the like. Examples of an amorphoussemiconductor constituting the amorphous semiconductor layer can includean i-type amorphous silicon, an n-type amorphous silicon, a p-typeamorphous silicon, and the like. The transparent conductive layer ispreferably formed of transparent conductive oxide in which tin (Sn),antimony (Sb) or the like is doped in metal oxide such as indium oxide(In₂O₃) and zinc oxide (ZnO).

In this embodiment, an n-type single crystal silicon substrate isapplied to the semiconductor substrate. The photoelectric conversionsection has a structure in which an i-type amorphous silicon layer, ap-type amorphous silicon layer, and a transparent conductive layer aresequentially formed on the light receiving surface of the n-type singlecrystal silicon substrate, and an i-type amorphous silicon layer, ann-type amorphous silicon layer, and a transparent conductive layer aresequentially formed on the rear surface of the substrate. Alternatively,the p-type amorphous silicon layer may be formed on the rear surfaceside of the n-type single crystal silicon substrate, and the n-typeamorphous silicon layer may be formed on the light receiving surfaceside of the substrate. That is, the photoelectric conversion section hasa junction of semiconductors having different optical gaps(heterojunction). An amorphous silicon layer (thickness: several nm toseveral tens of nm) forming a heterojunction generally absorbs lighthaving a wavelength of 600 nm or less.

For the first protection member 12, a member having transparency such asa glass substrate, a resin substrate and a resin film can be used. Amongthese, from a viewpoint of fire resistance, durability, and the like,the glass substrate is preferably used. The thickness of the glasssubstrate is not particularly limited, but is preferably about 2 mm to 6mm.

For the second protection member 13, a transparent member which is thesame as the first protection member 12 may be used, or an opaque membermay be used. In this embodiment, a resin film is used as the secondprotection member 13. The resin film is not particularly limited, but ispreferably a polyethylene terephthalate (PET) film. From a viewpoint oflowering moisture permeability and the like, in the resin film, aninorganic compound layer of silica or the like, or a metal layer ofaluminum or the like may be formed in a case where it is not assumedthat light is incident from the rear surface side. The thickness of theresin film is not particularly limited, but is preferably about 50 μm to300 μm.

The encapsulant layer 14 plays a role in preventing moisture and thelike from coming into contact with the solar cells 11. The encapsulantlayer 14 is also called a sealing layer (sealant). The encapsulant layer14 is formed, for example, by a lamination step described below, by useof two respective resin sheets constituting the encapsulant layers 14 a,14 b. In this embodiment, the encapsulant layers 14 a, 14 b are closelyadhered to each other between the solar cells 11, and between ends ofthe solar cell panel 16 and the solar cells 11 near the ends. Thethickness of the encapsulant layer 14 is not particularly limited, andthe thickness of each of the encapsulant layers 14 a, 14 b is preferablyabout 100 μm to 600 μm.

Hereinafter, the encapsulant layer 14 containing the wavelengthconversion substances 30 will be further described in detail withreference to FIG. 2. FIG. 2 is a sectional view of the solar cell panel16. In FIG. 2, the wavelength conversion substances 30 are illustratedby white circles.

As illustrated in FIG. 2, the wavelength conversion substances 30 arecontained in the encapsulant layer 14 a provided on at least the lightreceiving surface side of the solar cells 11. That is, the wavelengthconversion substances 30 may be contained only in the encapsulant layer14 a (in this case, the concentration of the wavelength conversionsubstances 30 satisfies, of course, concentration in encapsulant layer14 a>concentration in encapsulant layer 14 b). The wavelength conversionsubstances 30 may be contained in the encapsulant layer 14 b provided onthe rear surface side of the solar cells 11, but the concentration ofthe wavelength conversion substances 30 in the encapsulant layer 14 a ishigher than the concentration of the wavelength conversion substances 30in the encapsulant layer 14 b. When the wavelength conversion substances30 are inorganic wavelength conversion substances, the concentration ofthe wavelength conversion substances 30 in the encapsulant layer 14 ais, for example, 0.1 weight percent to 15 weight percent, and morepreferably 1.5 weight percent to 10 weight percent. In a case of organicwavelength conversion substances, the concentration of the wavelengthconversion substances 30 is, for example, 0.02 weight percent to 2.0weight percent, and more preferably 0.05 weight percent to 0.8 weightpercent.

Resin constituting the encapsulant layer 14 (encapsulant layers 14 a, 14b) is preferably excellent in adhesion to the respective protectionmembers and the solar cells 11, and highly impermeable to moisture. Morespecifically, examples of the resin constituting the encapsulant layerinclude olefin based resin obtained by polymerizing at least oneselected from α-olefin of 2-20C (for example, a random or blockcopolymer of polyethylene, polypropylene, ethylene, and other α-olefin),ester-based resin (for example, polycondensate of polyol andpolycarboxylic acid or acid anhydride/acid lower alkyl ester thereof),urethane-based resin (for example, a polyaddition product withpolyisocyanate and active hydrogen-containing compounds (such as diol,polyol, dicarboxylic acid, polycarboxylic acid, polyamine, polythiol)),epoxy-based resin (for example, opening polymer of polyepoxide, apolyaddition product with polyepoxide and the above activehydrogen-containing compound), and a copolymer of α-olefin, and vinylcarboxylate, acrylic ester, or other vinyl monomer.

Among these, the resin constituting the encapsulant layer isparticularly preferably olefin based resin (particularly, a polymercontaining ethylene), and a copolymer of α-olefin and vinyl carboxylate.As the copolymer of α-olefin and vinyl carboxylate, ethylene-vinylacetate copolymer (EVA) is particularly preferable. However, acombination of resin constituting the encapsulant layer 14 a(hereinafter, sometimes referred to as “resin 14 a”), and resinconstituting the encapsulant layer 14 b (hereinafter, sometimes referredto as “resin 14 b”) needs to satisfy the following relation.

For the resin 14 b, resin having a smaller diffusion coefficient of thewavelength conversion substances 30 than the diffusion coefficient ofthe resin 14 a is used. The diffusion coefficient is a factor ofproportionality which regulates the speed of diffusion appearing inFick's laws of diffusion. The diffusion coefficient of the wavelengthconversion substances 30 can be calculated by overlapping of a layerconstituted from resin which contains the wavelength conversionsubstances 30 and which is to be measured, and an olefin based resinlayer which does not contain the wavelength conversion substances 30,and obtaining the outflow speed of the wavelength conversion substances30 from the resin layer to be measured. The outflow speed can beobtained by quantity by Gas Chromatography, or transmission spectrummeasurement. The diffusion coefficient of the wavelength conversionsubstances 30 is made to satisfy diffusion coefficient of resin 14b<diffusion coefficient of resin 14 a, so that the wavelength conversionsubstances 30 contained in the encapsulant layer 14 a can be inhibitedfrom being diffused into the encapsulant layer 14 b.

The diffusion coefficient of the wavelength conversion substances 30 inthe resin 14 a is, for example, 1×10⁻¹² to 1×10⁻¹⁰ (m²/s) at 120° C. Thediffusion coefficient of the wavelength conversion substances 30 in theresin 14 b is, for example, 1×10⁻¹³ to 1×10⁻¹¹ (m²/s) at 120° C.

The resin 14 b preferably has a higher storage elastic modulus at 25° C.to 90° C. (hereinafter, simply referred to as a “storage elasticmodulus”) than that of the resin 14 a. The storage elastic modulus is aratio of elastic stress of the same phase as strain, and is representedby a real part of a complex modulus of elasticity. The larger a numeralvalue of the storage elastic modulus, the higher the elasticity ofresin. The storage elastic modulus of each resin 14 a, 14 b can bemeasured by use of a dynamic viscoelasticity measuring device. Thestorage elastic modulus satisfies the relation storage elastic modulusof resin 14 b>storage elastic modulus of resin 14 a, so that thediffusion coefficient of the wavelength conversion substances 30 easilysatisfies diffusion coefficient of resin 14 b<diffusion coefficient ofresin 14 a. The storage elastic modulus (value at a frequency of 10 Hzin a tension mode at 25° C.) of the resin 14 a is preferably 1×10⁷ to1×10⁸ (Pa), and the storage elastic modulus of the resin 14 b in thesame condition is 1×10⁸ to 1×10⁹ (Pa).

The resin 14 b preferably has a smaller intermolecular void size at 25°C. to 90° C. than that of the resin 14 a. In other words, the resin 14 bpreferably has a smaller free volume at 25° C. to 90° C. than that ofthe resin 14 a. The intermolecular void size means size of a void partwhich is not occupied by molecules (atoms). The intermolecular void sizeof each resin 14 a, 14 b can be measured by use of a positronannihilation method. The intermolecular void size satisfies void size ofresin 14 b<void size of resin 14 a, so that the diffusion coefficient ofthe wavelength conversion substances 30 easily satisfies void size ofresin 14 b<void size of resin 14 a. The intermolecular void size of theresin 14 a is preferably 0.08 nm³ to 0.12 nm³, and the intermolecularvoid size of the resin 14 b is preferably 0.05 nm³ to 0.09 nm³.

As long as the combination of the resins 14 a, 14 b satisfies the aboverelation, the combination is not particularly limited. The following isan example of the combination.

Example 1 resin 14 a; low-density polyolefin, resin 14 b: high-densitypolyolefin

Example 2 resin 14 a; low molecular weight polyolefin, resin 14 b: highmolecular weight polyolefin

Example 3 resin 14 a; low molecular weight EVA, resin 14 b: highmolecular weight EVA

The wavelength conversion substances 30 absorb, for example, ultravioletlight which is light having a wavelength shorter than 380 nm, andconvert the ultraviolet light into light having a longer wavelength(e.g., 400 nm to 800 nm). In this case, the wavelength conversionsubstances 30 contribute to inhibition of deterioration of componentmaterials due to the ultraviolet light. The wavelength conversionsubstances 30 are preferably substances that absorb ultraviolet light toemit visible light, but may be substances that absorb visible light orinfrared light. Generally, the wavelength conversion substances 30convert light having a shorter wavelength into light having a longerwavelength, but may convert light having a longer wavelength into lighthaving a shorter wavelength, namely, cause so-called up-conversion lightemission. The preferable conversion wavelength varies depending on thetype of the solar cells 11.

In this embodiment, the solar cells 11 each have a heterojunction layer(amorphous semiconductor layer), and therefore the wavelength conversionsubstances 30 preferably absorb light having energy larger than a bandgap of the heterojunction layer to convert the wavelength. That is, thewavelength conversion substances 30 preferably convert the light havingthe wavelength absorbed in the heterojunction layer. For example, thewavelength conversion substances 30 are used to absorb light having awavelength λ_(α) absorbed by an amorphous semiconductor layer and toconvert the light having a wavelength λ_(α) into light having awavelength λ_(β) which is not absorbed in the semiconductor layer. Thewavelength λ_(α) is 600 nm or less.

Specific examples of the wavelength conversion substances 30 includesemiconductor nanoparticles (quantum dots), inorganic compounds such asa luminescent metal complex, and organic compounds such as an organicfluorescence dye. Examples of the semiconductor nanoparticles caninclude zinc oxide (ZnO) nanoparticles, cadmium selenide (CdSe)nanoparticles, cadmium telluride (CdTe) nanoparticles, gallium nitride(GaN) nanoparticles, yttrium oxide (Y₂O₃) nanoparticles, and indiumphosphide (InP) nanoparticles. Examples of the luminescent metal complexcan include Ir complexes such as [Ir(bqn)₃](PF₆)₃, [Ir(dpbpy)₃](PF₆)₃,Ru complexes such as [Ru(bqn)₃](PF₆)₃, [Ru(bpy)₃](ClO₄)₂, Eu complexessuch as [Eu(FOD)₃]phen, [Eu(TFA)₃]phen, and Tb complexes such as[Tb(FOD)₃]phen, [Tb(HFA)₃]phen. Examples of the organic fluorescence dyecan include a rhodamine dye, a coumarin dye, a fluorescein dye, and aperylene dye.

The wavelength conversion substances 30 substantially uniformly disperseinto, for example, the encapsulant layer 14 a. The encapsulant layer 14a may contain ultraviolet light absorbing substances that absorbultraviolet light and do not emit light. In this case, there may be anuneven concentration distribution of the wavelength conversionsubstances 30 in the encapsulant layer 14 a. For example, theconcentration of the wavelength conversion substances 30 near the firstprotection member 12 may be made higher than the concentration of thewavelength conversion substances 30 near the solar cells 11.Additionally, two or more kinds of the wavelength conversion substances30 may be added to the encapsulant layer 14 a, or there may be an unevenconcentration distribution of each wavelength conversion substance 30 inthe encapsulant layer 14 a.

The solar cell module 10 having the above configuration can bemanufactured by laminating the string of the solar cells 11 connected bythe wiring materials 15 by use of resin sheets constituting the firstprotection member 12, the second protection member 13, and theencapsulant layer 14. In a laminating device, for example, the firstprotection member 12, the resin sheet constituting the encapsulant layer14 a, the string of the solar cells 11, the resin sheet constituting theencapsulant layer 14 b, and the second protection member 13 aresequentially laminated on a heater. The resin sheet constituting theencapsulant layer 14 a contains the wavelength conversion substances 30therein. This laminated body is heated to about 150° C., for example, ina vacuum state. Thereafter, the laminated body continues to be heatedunder atmospheric pressure while respective components are pressed ontothe heater side, and the resin composition of the resin sheet iscrosslinked, so that the solar cell panel 16 is obtained. Finally, theframe 17 and the like are mounted on the solar cell panel 16, so thatthe solar cell module 10 is obtained.

As described above, according to the solar cell module 10 having theabove configuration, the wavelength conversion substances 30 in theencapsulant layer 14 a disposed on the light receiving surface side ofthe solar cells 11 can be inhibited from being diffused into theencapsulant layer 14 b disposed on the rear surface side of the solarcells 11. That is, in the solar cell module 10, the high concentrationof the wavelength conversion substances 30 is maintained in theencapsulant layer 14 a upon which a large quantity of light is incident,for a long period. Consequently, it is possible to improve efficiency ofutilization of incident light, and improve photoelectric conversionefficiency.

Second Embodiment

Hereinafter, with reference to FIG. 3 and FIG. 4, a solar cell module 50of a second embodiment will be described in detail. FIG. 3 is asectional view of a solar cell panel 51 constituting the solar cellmodule 50. FIG. 4 is a plan view illustrating an extracted diffusioninhibiting layer 52 constituting the solar cell module 50. Hereinafter,differences from the first embodiment will be mainly described, withcomponents similar to the components of the first embodiment beingdenoted by the same reference numerals, and repeated description omitted(the same applies to a third embodiment).

As illustrated in FIG. 3, the solar cell module 50 is different from thesolar cell module 10 in that the diffusion inhibiting layer 52 whichinhibits diffusion of wavelength conversion substances 30 is providedbetween an encapsulant layer 14 a and an encapsulant layer 14 b. Thediffusion inhibiting layer 52 is preferably interposed between bothlayers over substantially the whole area such that the encapsulant layer14 a is not in contact with the encapsulant layer 14 b. The diffusioninhibiting layer 52 is provided, for example, between voids of adjacentsolar cells 11, between ends of the solar cell panel 51 and the solarcells 11 near the ends.

The diffusion inhibiting layer 52 is formed of a material having asmaller diffusion coefficient of the wavelength conversion substances 30than that of the resin 14 a. In this embodiment, the diffusioninhibiting layer 52 is formed by use of a resin sheet which does nothave a metal layer and an inorganic compound layer, and a resinconstituting the diffusion inhibiting layer 52 (hereinafter, sometimesreferred to as “resin 52”) has wavelength conversion substances 30 ofsmaller diffusion coefficient than in the resin 14 a. The resin 52preferably has a higher storage elastic modulus than that of the resin14 a, and preferably a smaller intermolecular void size than that of theresin 14 a. The relation of the resin 14 a and the resin 52 is the sameas the relation of the resin 14 a and the resin 14 b in the firstembodiment, for example. Furthermore, the resin 52 preferably haswavelength conversion substances 30 of smaller diffusion coefficientthan in the resin 14 b.

As illustrated in FIG. 4, the diffusion inhibiting layer 52 is formed ofa resin sheet formed with through holes 53 at portions where the solarcells 11 are disposed, and the resin sheet is preferably provided to beinterposed between a resin sheet constituting the encapsulant layer 14 aand a resin sheet constituting the encapsulant layer 14 b. In thisembodiment, the solar cells 11 each have a shape formed by obliquelycutting four corners of a substantial square in plan view, and thethrough holes 53 each have a shape which is substantially the same asthe solar cell 11. The through holes 53 are formed to correspond to thenumber of the solar cells 11 (eight in the example illustrated in FIG.4). In the diffusion inhibiting layer 52, the through holes 53 may beformed so as to be larger than the solar cells 11 and may be provided soas not to overlap with the solar cells 11. However, the through holes 53are preferably formed so as to be slightly smaller than the solar cells11 and so as not to overlap with the end edges of the solar cells 11.

According to the solar cell module 50 having the above configuration,similarly to the solar cell module 10, the wavelength conversionsubstances 30 in the encapsulant layer 14 a can be inhibited from beingdiffused on the rear surface side of the solar cells 11. Furthermore, ina case of the solar cell module 50, the diffusion inhibiting layer 52inhibits diffusion of the wavelength conversion substances 30, andtherefore design freedom of the encapsulant layer 14 b is improvedcompared to the case of the solar cell module 10.

Third Embodiment

Hereinafter, with reference to FIG. 5, a solar cell module 60 of a thirdembodiment will be described in detail. FIG. 5 is a sectional view of asolar cell panel 61 constituting the solar cell module 60, andillustrates a void portion between adjacent solar cells 11.

As illustrated in FIG. 5, the solar cell module 60 is similar to thesolar cell module 50 in that a diffusion inhibiting layer 62 whichinhibits diffusion of wavelength conversion substances 30 is providedbetween an encapsulant layer 14 a and an encapsulant layer 14 b. On theother hand, the solar cell module 60 is different from the solar cellmodule 50 in that the diffusion inhibiting layer 62 is constituted by aresin layer 63 and a metal layer 64. Resin constituting the resin layer63 is not particularly limited, and may be, for example, resin similarto the resin 14 a, 14 b.

Metal constituting the metal layer 64 of the diffusion inhibiting layer62 has a diffusion coefficient of the wavelength conversion substances30 which is substantially zero (smaller diffusion coefficient of thewavelength conversion substances 30 than in the resin 14 a). Therefore,the diffusion inhibiting layer 62 is interposed between the encapsulantlayer 14 a and the encapsulant layer 14 b over substantially the wholearea, so that it is possible to significantly inhibit diffusion of thewavelength conversion substances 30 to the encapsulant layer 14 b. Themetal constituting the metal layer 64 has a higher storage elasticmodulus than that of the resin 14 a.

In the example illustrated in FIG. 5, on the light receiving surfaceside of the solar cells 11, the diffusion inhibiting layer 62 isdisposed so as to overlap with end edges of the solar cells 11. Thediffusion inhibiting layer 62 may be disposed on the rear surface sideof the solar cells 11. In either case, from a viewpoint of insulationsecurement, the diffusion inhibiting layer 62 is disposed such that theresin layer 63 is on the solar cell 11 side. The metal layer 64functions as, for example, a reflection layer which diffuses andreflects incident light passing from voids between the solar cells 11 tothe rear surface side, and allows the light to be incident upon thesolar cells 11 again. In order to facilitate diffusion and reflection oflight, irregularities may be formed on a surface of the metal layer 64.

The design of each embodiment can be suitably changed without departingfrom the object of the present disclosure.

For example, the diffusion inhibiting layer 52 is provided by use of theresin sheet having the through holes 53 in the above embodiment, but maybe a diffusion inhibiting layer by use of a resin sheet having nothrough hole, or by disposing a plurality of strip-shaped sheets in thevoids between the solar cells 11. Additionally, the diffusion inhibitinglayer may have an inorganic compound layer of silica or the like, inplace of the metal layer 64.

REFERENCE SIGNS LIST

-   10, 50, 60 Solar cell module-   11 Solar cell-   12 First protection member-   13 Second protection member-   14, 14 a, 14 b Encapsulant layer-   15 Wiring material-   16, 51, 61 Solar cell panel-   17 Frame-   30 Wavelength conversion substance-   52, 62 Diffusion inhibiting layer-   53 Through hole-   63 Resin layer-   64 Metal layer

1. A solar cell module comprising: a solar cell; a first protectionmember provided on a light receiving surface side of the solar cell; asecond protection member provided on a rear surface side of the solarcell; an encapsulant layer that includes a first encapsulant layerdisposed between the solar cell and the first protection member, and asecond encapsulant layer disposed between the solar cell and the secondprotection member, and seals the solar cell; and a wavelength conversionsubstance that is contained in at least the first encapsulant layer,wherein concentration of the wavelength conversion substance in thefirst encapsulant layer is higher than concentration of the wavelengthconversion substance in the second encapsulant layer, and (

) a diffusion inhibiting layer constituted from a material having asmaller diffusion coefficient of the wavelength conversion substancethan he diffusion coefficient of resin constituting the firstencapsulant layer is provided between the first encapsulant layer andthe second encapsulant layer.
 2. The solar cell module according toclaim 1, wherein the material constituting the diffusion inhibitinglayer has a higher storage elastic modulus at 25° C. to 90° C. than thatof the resin constituting the first encapsulant layer.
 3. The solar cellmodule according to claim 1, wherein the material constituting thediffusion inhibiting layer has a smaller intermolecular void size at 25°C. to 90° C. than that of the resin constituting the first encapsulantlayer.
 4. The solar cell module according to claim 1, wherein thewavelength conversion substance is an inorganic semiconductornanoparticle.
 5. The solar cell module according to claim 1, wherein thewavelength conversion substance is a luminescent metal complex.
 6. Thesolar cell module according to claim 1, wherein the wavelengthconversion substance is a fluorescence dye.
 7. The solar cell moduleaccording to claim 1, wherein concentration of the wavelength conversionsubstance in a first region of the first encapsulant layer closer to thefirst protection member is higher than in a second region of the firstencapsulant layer closer to the solar cell.
 8. The solar cell moduleaccording to claim 1, wherein a front surface side of the diffusioninhibiting layer has concave-convex pattern arranged in width directionof the diffusion inhibiting layer, and the front surface side is facesthe first encapsulant layer.
 9. The solar cell module according to claim1, wherein the diffusion inhibiting layer comprising a metal layer at afront surface side of the diffusion inhibiting layer, and the frontsurface side is faces the first encapsulant layer.
 10. The solar cellmodule according to claim 9, wherein the resin layer of the diffusioninhibiting layer is arranged between the metal layer and the solar cell,and the metal layer and the solar cell are insulated each other.
 11. Thesolar cell module according to claim 1, wherein the diffusion inhibitinglayer comprising an inorganic compound layer at the front surface sideof the diffusion inhibiting layer.